Injection devices

ABSTRACT

When the injection device is applied to a patient&#39;s skin and a plunger is pressed, the entire syringe and a carrier move forwards in relation to a barrel such that ribs on the carrier snap past a rib on a shroud. The syringe is arrested by flanges coming up against the rib, and a spring is compressed and a needle is fully projected. Further pressing on the plunger ejects the dose. The needle shroud is kept at the rearward position by its firm engagement around the injection area. On withdrawal of the device, the shroud is pushed forwards by the spring to protect the needle. This draws fingers through gaps in the ribs, the fingers being forced to bend towards the fingers as the divergence takes effect.

[0001] This invention relates to medical injection devices. It isconcerned with those in which a syringe is within a housing, initiallyfully encased, but once the housing is uncapped it can be moved forwardsfor the needle to be projected and for the dose to be administered. Theuser holds the housing rather than the syringe itself.

[0002] It is known to have a needle shroud carried by the housing whichafter injection can be shifted to a position concealing the needle. Itis important that such a shroud should not then be moved, riskingre-exposure of the needle. It is the aim of this invention to provide asimple and reliable way of locking such a shroud automatically to itshousing.

[0003] According to the present invention there is provided an injectiondevice for a syringe, the device comprising a housing for the syringewith a forwardly biased needle shroud at its leading end capable ofmovement between forward and rearward positions, the syringe duringinjection being moved forwards to project its needle beyond the shroudin its rearward position, and the shroud, moved to its forward positionconcealing the needle after injection, being prevented from reversion toits rearward position by snap-engagement with part of the housing.

[0004] Preferably, the shroud will telescope into a barrel-like housing.It can have at least one rearwardly extending finger that extends pastan abutment within the housing, that finger being flexed as the shroudmoves forwards for its tip to move past the abutment. Thereupon thefinger springs back to its natural configuration with its tip in frontof the abutment, thereby preventing the shroud moving backwards.

[0005] Conveniently, this flexing of the finger will be circumferential,in which case there must be means for preventing the shroud rotatingwith respect to the housing if those two members are bodies ofrevolution. These means may be combined with means for preventingcomplete withdrawal of the shroud from the housing. A further, longerfinger may be associated with and divergent from the or each firstfinger, both fingers of a pair passing through a common gap in theabutment within the housing. This further finger may have a hookformation at its rear, free end, and this will effectively engage behindthe abutment when the shroud reaches its forward position. As it movestowards that, the fingers are squeezed together by the sides of the gapuntil the first, shorter finger clears the gap and springs away from thesecond, longer finger.

[0006] The abutment within the housing may also serve to locate acarrier for the syringe before injection, and it can also provide alimit to the forward movement of the capsule of the syringe.

[0007] In the preferred form, the housing will have a cap, removableforwardly for use of the device, with a tubular portion that extendsback into the housing to co-operate with the carrier and prevent thatdisengaging from the abutment. In other words, it keeps the carrierlocated in its pre-injection position and prevents premature operation.But once the cap is removed, the carrier will be capable ofdisengagement from the abutment.

[0008] For a better understanding of the invention, one embodiment willnow be described, by way of example, with reference to the accompanyingdrawings, in which:

[0009] FIGS. 1 to 6 are axial sections of an injection device showing itin various stages from pre-use to post-use,

[0010]FIG. 7 is a perspective view of a needle shroud forming part ofthe injection device,

[0011]FIG. 8 is a cross-section on the line VIII-VIII of FIG. 3,

[0012]FIG. 9 is a perspective view of a syringe carrier forming part ofthe device, and

[0013]FIG. 10 is a cutaway perspective view of the injection device.

[0014] The injection device to be described is intended to form part ofan auto-injection system. A spring-loaded drive mechanism will beattached to the rear end of the device, and when released or fired itwill act on the syringe within the device to thrust that forward andeject the dose. Such drive mechanisms are known and therefore they arenot illustrated and are not described in detail.

[0015] The injection device has a cylindrical barrel 1 initially closedat its leading end by an elongate cap 2. This has a relatively shortouter tubular section 3 which plugs into the barrel 1, being limited byan annular rib 4, and a much longer re-entrant tubular section 5 whichinitially extends back into the barrel to encase about three quartersthe length of a syringe 6. This is of conventional form with a capsule 7having a rear end flange 8 beyond which a plunger 9 extends, while atthe reduced leading end there is a needle assembly 10 with the needle 11concealed within a sheath 12. The interior of the re-entrant portion 5has an annular rib 13 of triangular section which, on assembly, can snappast the enlarged base of the sheath and engage behind it.

[0016] Surrounding the forward half of the re-entrant portion 5 in theinitial state of the device is a tubular needle shroud 14. This stepsout at a shoulder 15 into a short rear tubular section 16, from whosefree rim there project rearwardly two pairs of fingers 17 and 18, one ofwhich is best seen in FIG. 7. The finger 17 is the longer, is axiallyparallel, and terminates at its rear end in a bifurcation with outwardlyprojecting barbs 19. The shorter finger 18 has a plain end, and itdiverges circumferentially slightly from the finger 17. Initially, boththese pairs of fingers extend through diametrically opposed gaps 20 inan annular rib 21 on the inside of the barrel 1, as shown in the detailof FIG. 8. The plastics material of which the needle shroud 14 is madeallows the fingers 18 to be flexed towards the associated fingers 17, toallow them to pass through the gaps 20 on assembly.

[0017] Surrounding the rear end of the capsule 6, with the intermediaryof a resilient bush 22, there is a syringe carrier 23, as best seen inFIG. 9. This has a short cylindrical portion 24 with two outward almostsemi-circular flanges 25 at its rear end between whose ends there arestuds 26 creating gaps 27 and 28. Two pairs of diametrically opposedfingers 29 and 30 project from the forward end of the portion 24, thefingers 29 being wider in the circumferential direction than the gaps 20and externally terminating in angled teeth 31 with a rounded rib 32 ashort distance to the rear of each tooth 31. The bevel or angle on theforward side is to aid assembly, when the teeth are snapped past the rib21. The fingers 30 of the other pair are somewhat narrower, slightlylonger, and terminate in inward flanges 33 with a rebate 34 in theoutside of each corner between finger 30 and flange 33. The radial facesof these rebates 34 are co-planar with the ends of the fingers 29. Ahelical spring 35 has its rear end located by these rebates 34 and alsobears against the ends of the fingers 29 while its forward end actsagainst the shoulder 15. As assembled, the fingers 29 and 30 overlap therear end of the re-entrant portion 5, and the teeth 31 and ribs 32engage around the rib 21 on either side of the gaps 20. The ends of thefingers 17 extend through the gaps 27 and their barbs 19 hook behind theflanges 25 and studs 26 of the syringe carrier 23. The tips of thefingers 18 are opposite the gaps 28 and the spring 35 is relaxed.

[0018] To prepare the device for use, the cap 2 is removed as shown inFIGS. 2 and 3. By virtue of the rib 13 engaging behind the sheath 12,that is drawn off the needle 11. During the initial freeing of thesheath 12 the rear end of the portion 5 still overlaps the fingers 29,thereby preventing them from flexing inwards and keeping the ribs 32engaged with the rear side of the rib 21. The carrier 23 is nottherefore tugged forwards with the sheath 12. But once that sheath isfreed from the needle assembly 10, the internal backing of the fingers29 by the portion 5 is no longer there, making it possible for thosefingers to flex inwardly.

[0019] Also initially, the needle shroud 14 cannot move backwardsbecause the rear end of the portion 16 is up against the rib 21, and itcannot move forwards since the barbs 19 are hooked behind the flanges 25and studs 26 of the immobilised syringe carrier 23.

[0020] The device is then applied to the patient's skin and the plunger9 pressed. This pushes the entire syringe and the carrier 23 forwards inrelation to the barrel 1 by virtue of the effective solidity of the dosewithin the capsule, the ribs 32 snapping passed the rib 21 at thecommencement of this movement. The syringe is arrested by the flanges 25coming up against the rib 21, the spring 35 now being compressed and theneedle 11 fully projected. Further pressing on the plunger 9 ejects thedose. The needle shroud 14 is kept at its original rearward position byits firm engagement around the injection area.

[0021] On withdrawal of the device, the needle is protected by theshroud 14 being pushed forwards by the spring 35 to the position shownin FIG. 6. This draws the fingers 17 and 18 through the gaps 20, thefingers 18 being forced to bend towards the fingers 17 as the divergencetakes effect. But once the fingers 18 have passed the rib 21, theyspring back to their natural straight condition. This means that theywill abut the rib 21 if any attempt is made to push the shroud 14backwards again. At the same time the barbs 19 re-engage the rear end ofthe syringe carrier 23 whose flanges 25 are up against the rib 21, thusthwarting any attempt that may be made to pull the needle shroud clearof the barrel. The shroud 14 is therefore trapped, the needle 11 safelywithin.

1. An injection device for a syringe, the device comprising a housingfor the syringe with a forwardly biased needle shroud at its leading endcapable of movement between forward and rearward positions, the syringeduring injection being moved forwards to project its needle beyond theshroud in its rearward position, and the shroud, moved to its forwardposition concealing the needle after injection, being prevented fromreversion to its rearward position by snap-engagement with part of thehousing.
 2. An injection device according to claim 1, wherein the shroudtelescopes into a barrel-like housing.
 3. An injection device accordingto claim 1, wherein the shroud has at least one rearwardly extendingfinger that extends past an abutment within the housing, that fingerbeing flexed as the shroud moves from the rearward to the forwardposition, for its tip to move past the abutment, the finger beinglocated to spring back to its natural configuration with its tip infront of the abutment, thereby preventing the shroud moving backwards,after the shroud has moved back to the forward position.
 4. An injectiondevice according to claim 3, wherein flexing of the finger iscircumferential.
 5. An injection device according to claim 4, whereinanti-rotation means is provided for preventing the shroud rotating withrespect to the housing if those two members are bodies of revolution. 6.An injection device according to claim 5, wherein the anti-rotationmeans is combined with means for preventing complete withdrawal of theshroud from the housing.
 7. An injection device according to claim 3,wherein a further, longer finger is associated with and divergent fromthe or each first finger, the first and further fingers of the pairpassing through a common gap in the abutment within the housing.
 8. Aninjection device according to claim 7, wherein the further finger has ahook formation at its rear, free end, which will effectively engagebehind the abutment when the shroud reaches its forward position.
 9. Aninjection device according to claim 3, wherein the abutment within thehousing serves to locate a carrier for the syringe before injection. 10.An injection device according to claim 9, wherein the abutment withinthe housing provides a limit to the forward movement of the capsule ofthe syringe.
 11. An injection device according to claim 9, wherein thehousing has a cap, removable forwardly for use of the device, with atubular portion that extends back into the housing to co-operate withthe carrier and prevent that disengaging from the abutment. 12.(cancelled)
 13. (cancelled)
 14. An injection device according to claim2, wherein the shroud has at least one rearwardly extending finger thatextends past an abutment within the housing, that finger being flexed asthe shroud moves from the rearward to the forward position, for its tipto move past the abutment, the finger being located to spring back toits natural configuration with its tip in front of the abutment, therebypreventing the shroud moving backwards, after the shroud has moved backto the forward position.
 15. An injection device according to claim 4,wherein a further, longer finger is associated with and divergent fromthe or each first finger, the first and further fingers of the pairpassing through a common gap in the abutment within the housing.
 16. Aninjection device according to claim 5, wherein a further, longer fingeris associated with and divergent from the or each first finger, thefirst and further fingers of the pair passing through a common gap inthe abutment within the housing.
 17. An injection device according toclaim 6, wherein a further, longer finger is associated with anddivergent from the or each first finger, the first and further fingersof the pair passing through a common gap in the abutment within thehousing.
 18. An injection device according to claim 10, wherein thehousing has a cap, removable forwardly for use of the device, with atubular portion that extends back into the housing to co-operate withthe carrier and prevent that disengaging from the abutment.